Recuperative type heat exchanger



Nov. 15, 1966 1.. R. WOSIKA RECUPERATIVE TYPE HEAT EXCHANGER 5 Sheets-Sheet 1 Filed Sept. 18, 1964 INVENTOR LEON R. WOS/KA 3 t r g on om 7 mm BY M, Mr M ATTORNEYS Nov. 15, 1966 L. R. WOSIKA 3,285,326

RECUPERATIVE TYPE HEAT EXCHANGER Filed Sept. 18, 1964 5 Sheets-Sheet 2 INVENTOR LEON R. WOS/KA /MVMWQM ATTORNEYS Nov. 15, 1966 L. R. WOSIKA 3 2 ,3

RECUPERATIVE TYPE HEAT EXCHANGER Filed Sept. 18, 1964 5 Sheets-Sheet 5 l 5 j INVENTOR LEON R. WOS/KA ATTORNEYS Nov. 15, 1966 R. WOSIKA RECUPERATIVE TYPE HEAT EXCHANGER INVENTOR LEON R. WOS/KA 5 Sheets-Sheet 4 Filed Sept. 18, 1964 ATTORNEYS Nov. 15, 1966 L. R. WQSIKA ,3

RECUPERATIVE TYPE HEAT EXCHANGER Filed Sept. 18, 1964 5 Sheets-Sheet 5 INVENTOR LEON R. 02 05/164 BY M 7644 a fi ATTORNEYS United States Patent 3,285,326 RECUPERATIVE TYPE HEAT EXCHANGER Leon R. Wosika, San Diego, Calif., assignor to International Harvester Company, San Diego, Calif., 21 corporation of New Jersey Filed Sept. 18, 1964, Ser. No. 397,564 6 Claims. (Cl. 165-4) The present invention relates generally to heat exchange apparatus and more particularly to new and improved counterflow, wraparound recuperators and to methods for the manufacture of such apparatus.

While the invention is useful in combination with various types of power plants, it will be described in relation to a gas turbine, the prime mover per se being no part of the invention.

A heat exchanger of the recuperator type is used to improve the specific fuel consumption of a power plant by transferring otherwise waste heat from the exhaust gases to the combustion air to heat such air prior to its entry into the combustion chamber. For example, ambient air at 80 F. entering the power plant without a recuperator might be raised to say 480 F. through compression. The 480 F. air then is mixed with fuel and the mixture burned to create gas temperatures designed for the particular machine, say 1500 F. at the burner exit. Thus, suflicient fuel must be used to increase the temperature by more than 1000 F. However, by utilizing a recuperator, the temperature of the air may be raised to over 900 F. at the inlet to the combustor, thus requiring fuel to increase temperature only 600 F. to the desired 1500" F. working temperature. Thus a specific fuel consumption of say .62 lbs./h.p./ hr. for a non-recuperative engine may be reduced to a specific fuel consumption of .47 by use of a recuperator.

Thus it can be seen that an effective heat exchanger may improve the specific fuel consumption of an engine by as much as 20 to 50 percent. Early recuperators were of the stacked plate type of either crossflow or counterflow construction, and proved quite useful. However, they require considerable space, special supports, and complex ducting. Late-r designs of the wraparound type, i.e., with matrix and headering wrapped into an annular configuration, decreased the space required and the ducting necessary, and could readily be supported by engine structure. However, serious problems of maintaining separation of exhaust gas and incoming air at the entry and exist ends of the recuperator have limited the use of the wraparound concept. In attacking this problem the prior art has resorted to expensive headerings of complex geometry necessitating excessive design work and extensive fabricating procedures to preclude leakage.

Therefore, a primary object of the present invention is to provide an improved comparatively inexpensive counterflow wraparound recuperator formed by novel angled matrix core sheets and a simplified headering.

Another major object is the provision of a recuperator of simplified construction which eliminates many of the fabricating complexities inherent in prior devices of this type, thus providing a comparatively inexpensive recuperator.

A further important object is the provision of such a recuperator in which the headering is integral with the matrix and permits the use of simplified manifolding for both exhaust gases and compressed air.

Another object is the provision of a compact wraparound structure which may be installed on and supported by a gas turbine or other engine.

It is also an object of the present invention to provide novel methods for manufacturing wraparound heat exchangers.

3,285,326 Patented Nov. 15, 1966 Additional objects and advantages will become apparent as the description proceeds in connection with the accompanying drawings in which:

FIGURE 1 is a perspective view of a typical application of the recuperator of the subject invention as applied to a gas turbine unit of essentially conventional construction with parts being broken away to show details of construction;

FIGURE 2 is an enlarged fragmentary longitudinal section along line 22 of FIGURE 1;

FIGURE 3 is a fragmentary transverse section taken along line 3-3 of FIGURE 2;

FIGURE 4 is a perspective view of the heat exchanger core shown removed from the remainder of the apparatus;

FIGURE 5 is an enlarged perspective view of the portion of the headering used with the core assembly of FIG- URE 4;

FIGURES 6 and 7 are plan views of two of the components of the recuperator as they appear before assembly; and

FIGURE 8 is a semi-diagrammatic view of aparatus for fabricating the recuperator core.

While, as indicated above, the heat exchanger of the present invention is of general application, it will be disclosed herein as applied to a gas turbine since this is an environment in which it is expected to have its greatest utility. The turbine assembly shown in FIGURE 1 is of generally cylindrical configuration at the axis of which is a suitably mounted power take off shaft 20 supporting an air compressor 22 and a two stage turbine assembly 24. Referring to FIGURES 1 and 2, when, the turbine is in operation, the air is caused to flow by the compressor 22 through the inlet opening 26, through the compressor into a plenum chamber 28 then into the ducts 76, described below, and through the air passages of the recuperator of the present invention which is indicated generally at 30. After it passes through the recuperator 30 the heated air flows into the inlet end of the combustion chamber 32 where fuel is added and the mixture is ignited. The hot expanded combustion gases then pass through the turbine assembly 24, diffuse through a duct 36into a plenum chamber 38. The combustion gases then pass through the gas passagesof the recuperator 30 and are delivered to a front plenum chamber 40 and pass from the turbine through an outlet 42. In FIGURE 1, the air and gas flows are indicated by solid and dotted arrows, respectively.

The body of the recuperator is formed by oppositely angled corrugated sheets 44 and 46 (shown separately in FIGURES 6 and 7) separated by spirally wound fiat uncorrugated sheets 48 and 50 as explained in detail below. In a typical case where the inner diameter of the recuperator assembly is three to four feet, the sheets 44 and 46 will be approximately three to four mils in thickness. The corrugations 52 of the sheet 44 which provide the air passages in the completed unit, have a height of approximately .10" and a width of .08. The corrugations 54 of the sheet 46 which provide the gas passages are slightly larger and may have a height'of approximately .125 and a width of .12. It is a feature of this construction that the size of the corrugations may be readily varied without affecting the headering or requiring other modifications. Each .of the corrugations is -formed at an angle to the edge of the sheet, the angle illustrated being 60. It is to be understood, however, that the angle is not critical providing that the angle in the corrugations 52 in the sheet 44 is equal and opposite to the angle of the corrugations 54 in the sheet 46 throughout the wrap.

The recuperator core, which is shown separately in FIGURE 4, is preferably fabricated in the following mannerusing apparatus of the type shown in FIGURE 8. A cylindrical sheet metal liner 56, which forms the inner surface of the recuperator core, is secured on a rotatable mandrel 58. Rolls of the corrugated sheets 44 and 46 and the flat sheets 48 and 50 are placed in spindles suitably spaced about the axis of the mandrel 58 as shown in FIGURE 8. A pair of filler strips 60 and 62 having a maximum height the same as the height of the corrugations of the sheets 44 and '46, respectively, are then welded to the liner 56 at positions 180 apart. The free ends of the fiat sheets 48 and 50 are then attached to the liner 56 and the filler strips with the tapered edge of the latter adjacent the line of attachment of the sheets to the liner 56. The free ends of the corrugated sheets 44 and 46 are then welded to the thick ends of the respective filler strips. The mandrel 58 is rotated while the flat sheets 48 and 50 are 'held under tension, thus winding alternate layers of the corrugated and flat sheets around the liner 56.

This winding or wrapping process continues until the required core thickness is achieved. Then two more filler strips 60 and 62 are attached to the sheets 48 and 50 at positions 180 apart with the tapered edges of the outer filler pieces extending oppositely to the tapered edges of the inner filler pieces. The corrugated sheets 44 and 46 are then cut off and attached to the thick edges of the filler strips. The inner fiat sheet 48 is then brought across the filler strip and attached to the underlying flat sheet and the outer flat sheet 50 is wrapped around the assembly for several rotations then cut off and attached to itself to form a relatively rigid outer shell. The assembly may now be removed from the mandrel. Braze material may be applied as a powder or slurry and the assembly may then be brazed in a conventional manner to form a complete integral unit. Alternatively, application of the braze material may be made continuously during the wrapping process.

The relatively low cost of the completed core is due in large measure to the use of the foregoing method which in turn is made possible by the unique construction of the core.

During the wrapping process the tensioning of the fiat sheets alone assures a tight wrap without risk of deforming the corrugated sheets. Further the core can be made to any desired thickness without modification of the wrapping apparatus or of the components of which the core is constructed.

Further, the shape of the core may be readily varied by changing the configuration of the mandrel 58 and the inner liner 56 to provide substantially any desired noncylindrical form.

It will be apparent that fluid applied to one end of the assembly will enter all of the passages and follow a helical course through the core to the opposite end and that the helical course of alternate wraps will be oppositely disposed at equal angles with respect to the axis of the assembly.

The novel header ducts of the present invention are then applied to separate the gas and air at the entry and exit ends of the core and to direct each into a desired path. To ready the core for the reception of the header ducts, a series of V-shaped wedge cuts is made in each end of the core, a series of cuts at one end of the core being shown in FIGURE 4. The cuts are made at the same angle as the corrugations of the sheets so that the opposite sides 64 and 66 of each of the V-shaped cuts are parallel respectively, to the corrugations forming the air passages and the corrugations forming the gas passages. Accordingly, the surfaces 66 open the set of air passages and effectively block off the gas passages. The opposite effect is achieved by the opposite surface 64 generated by each cut. The portion of the core projecting outwardly beyond the base of the V-shaped cuts, forms a portion of the header structure, this structure being completed by the separate d-uct pieces.

Slots 68 and 70 are then out in the apex and vertex of each V-cut to receive the reduced ends of the long and short legs 72 and 74 of the duct pieces 76. After the duct pieces 76 are positioned as shown in FIGURE 5, they are brazed in place to form air tight joints. Preferably the slots 68 and 70 are first filled with steel wool or similar material to aid in the formation of tight seals in this region. The outer ends of each of the duct pieces are then closed and sealed by sheet metal plates 78 which are preferably welded in place. The outer surface of the recuperator assembly is completed by installing identical relatively heavy attaching flanges 80 and 82 provided with holes 84 for the reception of the bolts 86 by which the recuperator assembly is attached to the turbine structure.

The recuperator assembly is completed by the installation preferably by welding, of a pair of identical inner flanged rings 88 each having a series of holes 90 for the reception of attaching bolts 92. The rings 88 each are provided with a series of openings 94 which are aligned with and conform to the area defined by the bottom of the duct covers. From the foregoing it will be apparent that when the recuperator assembly is installed in the turbine as shown in FIGURE 1, the incoming air entering the plenum chamber 28 will pass through the adjacent openings 94 and into each one of the duct pieces 76 then through the corrugations provided by the sheet 44 and will follow a helical path into the duct pieces 76 at the opposite end of the recuperator for passage radially inwardly through the openings 94 into the combustion chamber.

Hot exhaust gases delivered to the plenum 38 will pass through the channels provided by the corrugations in the sheets 46, entering these channels through the spaces between the duct pieces 76. These gases will also pass helically through the recuperator and thence into the plenum 40 for passage ultimately through the outlet opening 42. Thus, adjacent ones of the corrugations carry air and gas passing through the heat exchanger in opposite directions in essentially counterflow relation. Since the corrugated and fiat sheets are fabricated of thin metal on the order of three to four mils thickness, they provide excellent heat exchange properties. The heat exchange efiiciency is further increased by the fact that both the air and combustion gases travel helically thus increasing the time in which the air and combustion gas are in heat exchange relation.

. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not re strictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A recuperator for a gas turbine having a body section enclosing a compressor, a turbine and a combustion chamber, an annular outlet scroll for combustion products projecting radially outwardly beyond said body section adjacent one end thereof, means forming a plenum chamber for combustion products adjacent the opposite end of said body section aligned with and axially spaced from said outlet scroll, means providing radially extending air passages connected to the outlet of said compressor and the inlet of said combustion chamber, respectively, said recuperator comprising an annular body surrounding said body section between said outlet scroll and said plenum chamber, said recuperator body having a plurality of narrow passages, alternate ones of said passages connecting said outlet scroll and said plenum chamher, and means connecting and remaining passages at their opposite ends to said radial air passages.

2. A recuperator for a gas turbine having a body section enclosing a compressor, a turbine and a combustion chamber, an annular outlet scroll for combustion products projecting radially outwardly beyond said body section adjacent one end thereof, means forming a plenum chamber for combustion products adjacent the opposite end of said body section aligned with and axially spaced from said outlet scroll, means providing radially extending air passages connected to the outlet of said compressor and the inlet of said combustion chamber, said recuperator body comprising sheets spirally wound upon themselves to provide a plurality of narrow passages, corrugated spacers positioned within said passages to maintain the radial width thereof, the corrugations of said passages extending helically, alternate ones of said passages being open at their opposite ends and connecting said outlet scroll to said plenum chamber, and means connecting the remaining passages adjacent their opposite ends to said radial air passages.

3. A heat exchanger comprising an annular body including two sets of corrugated layers, the axes of the corrugations of a given layer being inclined with respect to the axes of the next adjacent layer, uncorrugated sheets separating said layers, said body having V-shaped notches at its opposite ends, one surface of said notches being parallel to the axes of the corrugations of one set of layers and the other surface of said notches being parallel to the axes of the corrugations of the other set of layers whereby the corrugations of one set of layers are open only at one of said surfaces and the corrugations of the other set of layers are open only at the other of said surfaces, and duct structure secured to said body at its opposite ends enclosing one surface only of each of said notches.

4. An annular heat exchanger comprising a body having an inner liner, a pair of corrugated sheets spirally wound on said liner in alternate layers, the axes of the corrugations of one sheet being inclined with respect to the axes of the corrugations of the other sheet, a pair of uncorrugated sheets each spirally wound around the outer surface of one of said corrugated sheets, said body having V-shaped notches at its opposite ends, one surface of said notches being parallel to the axes of the corrugations of one of said sheets and the other surface of said notches being parallel to the axes of the corrugations of the other sheet whereby the corrugations of one of said sheets are open only at one of said surfaces and the corrugations of the other sheet are open only at the other of said surfaces, and duct structure secured to said body and enclosing one surface only of each of said notches.

5. A recuperator for a power plant having an air in- 5 let passage and a combustion products outlet passage, said recuperator comprising an annular body comprising a pair of spirally wound corrugated sheets, and a pair of spirally Wound uncorrugated sheets separating said corrugated sheets, said corrugated sheets providing passages extending helically from end to end of said body, means connecting the opposite ends of the helical passages of alternate sheets to said air inlet passages, and means connecting the opposite ends of the helical passages of the remaining sheets to said combustion products outlet passages.

6. A recuperative heat exchanger for a gas turbine having a body section enclosing a compressor, a turbine, and a combustion chamber, an annular outlet member for combustion products projecting radially outwardly beyond said body section adjacent one end thereof, means forming a plenum chamber for combustion products aligned with and axially spaced from said outlet member, means providing radially extending air passages connected to the outlet of said compressor and the inlet of said combustion chamber, respectively, said heat exchanger comprising a body including two sets of corrugated layers, the axes of the corrugations of a given layer being inclined with respect to the axes of the next adjacent layer, uncorrugated sheets separating said layers, said body having V-shaped notches at its opposite ends, one surface of said notches being parallel to the axes of the corrugations of one set of layers and the other surface of said notches being parallel to the axes of the corrugations or the other set of layers whereby the corrugations of one set of layers are open only at one of said surfaces, and duct structure secured to said body at its opposite ends enclosing one surface only of each of said notches, said duct structure being connected to said air passages, the other surface of each of said notches being in communication with said outlet and said plenum chamber, respectively.

References Cited by the Examiner UNITED STATES PATENTS Re. 19,140 4/1934 Frankl -10 2,136,086 11/1938 Rosenblad 165166 2,454,310 11/1948 Ganahl 165--66 X 2,887,456 5/1959 Halford et al. 252477 3,098,522 7/1963 McCormick 165-166 3,208,131 9/1965 Ruff 29-157 FOREIGN PATENTS 915,093 7/ 1946 France. 1,152,715 8/1963 Germany.

734,938 8/ 1955 Great Britain.

ROBERT A. OLEARY, Primary Examiner. M. A. ANTONAKAS, Assistant Examiner. 

5. A RECUPERATOR FOR A POWER PLANT HAVING AN AIR INLET PASSAGE AND A COMBUSTION PRODUCTS OUTLET PASSAGE, SAID RECUPERATOR COMPRISING AN ANNULAR BODY COMPRISING A PAIR OF SPIRALLY WOUND CORRUGATED SHEETS, AND A PAIR OF SPIRALLY WOUND UNCORRUGATED SHEETS SEPARATING SAID CORRUGATED SHEETS, SAID CORRUGATED SHEETS PROVIDING PASSAGES EXTENDING HELICALLY FROM END TO END OF SAID BODY, MEANS CONNECTING THE OPPOSITE ENDS OF THE HELICAL PASSAGES OF ALTERNATE SHEETS TO SAID AIR INLET PASSAGES, AND MEANS CONNECTING THE OPPOSITE ENDS OF THE HELICAL PASSAGES OF THE REMAINING SHEETS TO SAID COMBUSTION PRODUCTS OUTLET PASSAGES. 